Performance comparisons of STDD and FDD schemes for TDMA systems using NC-PRMA protocol

A new protocol called non-collision packet reservation multiple access (NC-PRMA) is introduced. Two kinds of duplexing schemes, frequency division duplexing (FDD) and shared time division duplexing (STDD), are taken into account. For the FDD scheme, each speech terminal is modeled as a two-state Markov process, whereas for the STDD scheme, each two-way conversation is characterized by a three-state Markov process. After modeling the offered traffic, the system performance measures, including channel throughput, mean access delay, and packet dropping probability are evaluated. In particular, the system capacities of both schemes are emphasized. The system capacity, denoted by M_0.01 is defined as the maximum number of conversations which can be supported under the constraint of packet dropping probability being no more than 1%. It is shown that the values of M_0.01 for the FDD and STDD schemes are about 38 and 45, respectively. This indicates that the STDD scheme achieves a significant improvement in system capacity relative to the FDD scheme. In addition, the numerical and simulation results show that our analytical approach yields reasonable accurate results